Aircraft hydraulic pressure simulating system



March 8, 1960 AIRCRAFT HYDRAULIC PRESSURE SIMULATING SYSTEM W. L. KON RAD Filed June 9, 1955 INVENTOR. William L. lnzzad H16 ATTORNEY United States Patent AIRCRAFT HYDRAULIC PRESSURE SIMULATING SYSTEM William L. Konrad, Pittsburgh, Pa., assignor to Westinghouse Air Brake Company, Wilmer-ding, Pa., a corporation of Pennsylvania Application June 9, 1955, erial No. 514,331

3 Claims. (Cl. 3512) This invention relates to flight simulators for pilot training, and particularlyto an improved selsyn system therefor.

ln flight trainers for transitional pilot training, it is important that the instrumentation of the trainer be made to'correspond with that found in the particular aircraft to be simulated. Further, in the operation of the trainer, it is desirable that the indications presented by the simulated instruments correspond with the indications of actual instruments under flight conditlons.

It is known to provide in such trainers a gauge simulating the pressure of the hydraulic systems supplying the servo motors which actuate the control surfaces in an actual aircraft. Basically, this pressure is controlledby a hydraulic pump which operates on a cycle which maintains the pressure between a maximum and minimum value.

Previously, it has been usual to simulate the operation of the pressure indicator for such a sys- 'tem by simply simulating the cyclic variations in pressponse to control movements made by the trainee in operating a simulator.

Accordingly, it is an'objectof my invention to provide an improved hydraulic pressure simulator.

It is a further object of my invention to provide an improved selsyn system for actuating the hydraulic pressure gauge in a transitional flight trainer.

It is a further object of my invention to provide an improved selsyn system for combining a plurality of signals.

It is a further object of my invention to provide an improved system for controlling a selsyn receiver in accordance with the rate of movement of a controlled object.

Other objects and further advantages of my invention will be apparent to those skilled in the art as the description proceeds. I

I shall first describe an embodiment of my invention, and shall then point out the novel features thereof in claims.

The drawing comprises a single figure showing a wiring diagram of one embodiment of my invention.

Referring to the drawing, the illustrated embodiment of my invention is adapted to be employed with a flight trainer having a pilots control stick 1 and a simulated hydraulic pressure gauge 39. Other details of the trainer may be conventional, and as they do not form a part of my present invention, they are not shown.

Hydraulic pressure indicator 39 has a needle 38 which is controlled through shaft 37 from rotor 22 of selsyn receiver 21. 'Selsyn 21 has a stator comprising windings 23, 32 and 33, which are connected to the stator winding 'ice' of a selsyn transmitter 30 through connections which will be hereinafter described. Selsyn transmitter 30 has a rotor 34 adapted to be driven through shaft 35 by a "conventional hydraulic pressure simulator 36. Rotors 22 and 34 are energized from a suitable source of alternating voltage as shown. I

Hydraulic pressure simulator 36 may be a conventional trainer component, adapted to provide a cyclic signal simulating the basic pumping cycle of the hydraulic system. The details of this component do not form a part H of the present invention and are, therefore, not shown.

minimum value.

However, for example, simulator 36 might comprise a motor having a conventional speed control adjusted in accordance with simulated engine speed, driving a cam to position shaft 35 cyclically between amaiiimum and Stator windingi29 of selsyn 30 is connected to stator winding 33 of selsyn 21 through'lead in serieswith resistor 27. Stator winding 28 of resolver 30 is icon 'nected to stator winding 32 throughdead 24 in series with resistor 26. Stator winding 31 0f resolver 39 is connected to stator winding 23 of resolver '21 through leads 19 and 20 in series with output windings 17 and 18 of a magneticv amplifier 11 for afpurpose to be described.

The function ofresistors 26 and 27" is to balance the impedance of windings 17 and 18.

' Magnetic amplifier 11 comprises a core 12 on which are wound output windings 17 and18, in opposition, and power windings 13 and 14' connected by jterminals :15 and 16 to a suitable" source of'alternating voltage.

A winding 10 is also placed on the core symmetrically with respect to the other windings. Asis well "known in the art, when there is 'no'bias voltage across winding 10, the voltages induced across windings 17 and 18 by windings 13 and 14 are 180 out of phase and there is no output voltage across leads 19 and 20. How- 'ever, if a DC. bias voltage appears across winding10,

at a particular instant one of 'windings 17 and 18 will be influenced by a flux at the saturation level, whereas the other winding will be influenced by a fiux'below the saturation level. Accordingly, an output voltage will appear across leads 19 and 20 proportional to the applied DC. voltage acros s'windingili.

' Winding 10 is connected across a potentiometer having 'a-wiper 8 and a resistor 7 through condenser 9. Re-

- sister 7 is connectedacrossbattery5throughresistor'6.

These components form a network 4 for producing an output voltage on wiper 8 which depends upon the position of the wiper. Wiper 8 is driven on resistor 7 by mechanical connection 3 from the pilots stick 1 which is pivoted to the framework of the simulator at 2.

The operation of this embodiment of my invention will now be described.

With stick 1 in a fixed position, and Wiper 8 stationary on resistor 7, no voltage will appear across winding 10 since under these conditions condenser 9 presents an infinite impedance. However, if stick 1 is moved in response to control movements by the trainee, a voltage will appear across Winding 10 proportional to the rate of movement of the stick. This signal will cause an output signal to appear across leads 19 and 20 proportional to the rate of movement of the pilots stick. Since leads 19 and 29 are in the circuit connecting selsyn transmitter 39 with selsyn receiver 21, the signal on leads 19 and 20 will be added to the signal introduced by the movement of rotor 34 of transmitter 30. Accordingly, the rotor 22 of .selsyn 21 will be positioned in accord ance with the sum of the pumping cycle signal and the transient signal introduced by stick movement. Needle 38 of indicator 39 will accordingly indicate a temporary drop in hydraulic pressure. i

' tion of condenser 9 in the system is not a perfect differentiation. Therefore, the signal appearing on the stator of resolver 21 maybe considered to consist of a component of the amplitude of the movement 'of 's'tick 1 as well as of the rate of movement. That is, in practice, it is found that the indication of needle 38 will be subject to a more pronounced variation when the stick is moved through a large angle than if moved through a small angle, even though atthe same rate. This. result is highly desirable, since in actual aircraft the pressure indicator is found 'to behave in substantially the :same'way.

While I have described an embodiment of my inveniion in detail, it will be obvious to those skilled in the :art'upon reading this disclosure that many changes and modifications in the disclosed structure could be made 'within the scope of my invention. Accordingly, I do :not wish tobe limited to .thedetails shown, but only-by the scope of the following claims.

Having thus described my invention, what I claim is: 1. A hydraulic pressure simulator for flight trainers, :comprising in combination, a hydraulic pressure indi- -cator, control means for said indicator, a magnetic amplifier connected tofprovide an output signal to saidcontrol 'means, a bias winding for determining the output signal of said amplifier, a potentiometer energized by a direct current voltage, a wiper jonsaid potentiometer, a

-condenser connected in series with said bias winding and :said wiper, the series circuit formed by said wiper, said condenser and said bias winding being connected across a portion of said potentiometer,'a pilots control member,

"and means mechanically connecting said pilots control memberto said wiper, movement of said control member causing a signal to be developed across said bias winding in accordance with the rate and extent of the movement of said pilots control member. 2. A hydraulic pressure simulator for flight trainers, comprising in combination, a selsyn transmitter and a selsyn receiver each having a stator and a rotor, means connecting a signal indicating pressure to said transmitter rotor, means connecting said stators to each other, a hydraulic pressure indicator positioned by said receiver rotor, a magnetic amplifier, an output Winding of said magnetic amplifier being connected to said stators, a bias winding for said amplifier, a potentiometer energized by a direct current voltage, a wiper on said potentiometer, a condenser connected in series with said bias winding and said wiper, said Wiper connecting said condenser and said bias winding across a portion of said potentiometer, a pilots control member, means mechanically connecting said pilots control member to said wiper, movement of said control member causing a'transient signal across said bias winding of said magnetic amplifier in accordance withthe rate and extent of the movement of said'control member, whereby said receiver rotor po sitions said hydraulic pressure indicator in accordance with the sum of said transient signal and said signal indicating pressure. 7 a

3. In a flight trainer, in combination, a pilots control member, a source of unidirectional voltage, a potentiometer connected across said source, a'wiper on said potentiometer mechanically connected tosaid pilotscontrol member, a magnetic amplifierhaving'a power winding,

control Winding and. output winding, said power winding being energized by a sourceof alternating voltage, a condenser connected inseries' Withsaid 'controlwinding and said wiper, the series circuit formed by said wiper, said condenser and said control winding being connected across a portion of said potentiometer, movement of said control member causing a transient signal to be developed across said control winding in accordance with the rate and extent of said movement, a selsyn transmitter having a stator and a rotor, a selsyn receiver also having a stator and a rotor, said rotors being energized by a source of alternating. voltage,'means pro viding a cyclic signal to said transmitter rotor, and means connectingrsaid selsyn transmitter stator and said magnetic amplifier output winding tosaid selsyn. receiver stator to position said receiver rotor in accordancewith the sum of said cyclic signal and said transient signal,

7 References Cited in the file of patent UNITED STATES-PATENTS 2,027,312 FitzGerald Jan. 7, 1936 2,458,586 Giraud Q Jamil, 1949 2,519,698 Pearsall V Aug..22, 1950 2,628,434 Dehmel Feb. 17, 1953 2,636,285 Fogarty et a1, Apr. 28, 1953 ,OTHER REFERENCES Electronic Analog Computers, (Korn and Korn). (Copy in Div. 23 and Scientific Library.) 

